Protective helmet



FIG. 1 perspective view of my new design for a protective helmet;

FIG. 2 is a left side elevation view thereof;

FIG. 3 is a right side elevation view thereof;

FIG. 4 is a back elevation view thereof;

FIG. 5 is a front elevation view thereof; and,

FIG. 6 is a top plan view thereof. 

CLAIM The ornamental design for a protective helmet, as shown and described. 